TY - JOUR

T1 - Adiabatic approach for heteronuclear SABRE hyperpolarization at high magnetic field

AU - Markelov, Danil A.

AU - Kozinenko, Vitaly P.

AU - Yurkovskaya, Alexandra V.

AU - Ivanov, Konstantin L.

N1 - This work was supported by the Russian Science Foundation (interdisciplinary projects #20-62-47038 and #20-63-47107 ). Публикация для корректировки.

PY - 2023/12

Y1 - 2023/12

N2 - Signal Amplification By Reversible Exchange (SABRE) is a technique aimed at enhancing weak NMR signals of heteronuclei by utilizing the non-equilibrium spin order of parahydrogen. SABRE polarization transfer takes place by means of metalorganic complexes that interact with parahydrogen and the substrate to be polarized in a reversible manner. To achieve substrate hyperpolarization in the high magnetic field of an NMR magnet, radiofrequency (RF) excitation is required. There are two general options for the RF field amplitude: constant or modulated. To date, there has been limited optimization of the adiabatic SABRE conditions. In SABRE, the presence of chemical exchange significantly complicates the spin dynamics involved in polarization transfer and the optimization of adiabatic RF sweeps. We conducted a comprehensive analysis of high-field SABRE pulse sequences with RF sweeps on the heteronuclear channel, specifically 15N. We proposed a simple method for optimizing the amplitude modulation profile of the RF field, which is efficient for systems undergoing chemical exchange. Our approach involved utilizing the dependence of 15N polarization on the amplitude of the constant RF field on the 15N channel. By employing the "optimal" adiabatic RF profile, we achieved a 2.5-fold increase in 15N SABRE-derived polarization at high magnetic field compared to a linear sweep. We theoretically assessed the benefit of RF sweeps over constant RF fields for SABRE at high magnetic field. We demonstrated experimentally that at temperatures −5∘C - +10∘C RF sweeps are more efficient than constant RF field. Maximal increase in 15N polarization achieved was 1.7-fold for bound and 1.4-fold for free substrate. We attribute this increase in polarization to the adiabaticity of the polarization transfer process. This behavior was explained via numerical solution of SABRE master equation for different dissociation rate constants.

AB - Signal Amplification By Reversible Exchange (SABRE) is a technique aimed at enhancing weak NMR signals of heteronuclei by utilizing the non-equilibrium spin order of parahydrogen. SABRE polarization transfer takes place by means of metalorganic complexes that interact with parahydrogen and the substrate to be polarized in a reversible manner. To achieve substrate hyperpolarization in the high magnetic field of an NMR magnet, radiofrequency (RF) excitation is required. There are two general options for the RF field amplitude: constant or modulated. To date, there has been limited optimization of the adiabatic SABRE conditions. In SABRE, the presence of chemical exchange significantly complicates the spin dynamics involved in polarization transfer and the optimization of adiabatic RF sweeps. We conducted a comprehensive analysis of high-field SABRE pulse sequences with RF sweeps on the heteronuclear channel, specifically 15N. We proposed a simple method for optimizing the amplitude modulation profile of the RF field, which is efficient for systems undergoing chemical exchange. Our approach involved utilizing the dependence of 15N polarization on the amplitude of the constant RF field on the 15N channel. By employing the "optimal" adiabatic RF profile, we achieved a 2.5-fold increase in 15N SABRE-derived polarization at high magnetic field compared to a linear sweep. We theoretically assessed the benefit of RF sweeps over constant RF fields for SABRE at high magnetic field. We demonstrated experimentally that at temperatures −5∘C - +10∘C RF sweeps are more efficient than constant RF field. Maximal increase in 15N polarization achieved was 1.7-fold for bound and 1.4-fold for free substrate. We attribute this increase in polarization to the adiabaticity of the polarization transfer process. This behavior was explained via numerical solution of SABRE master equation for different dissociation rate constants.

KW - Adiabatic process

KW - Heteronuclear NMR

KW - Hyperpolarization

KW - Parahydrogen induced polarization

KW - SABRE

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85178284970&origin=inward&txGid=5b2fb41d0fc2267cbb7f4eadfccd3624

UR - https://www.mendeley.com/catalogue/5fa90685-61a3-3b60-967e-b0e4da7830e1/

U2 - 10.1016/j.jmro.2023.100139

DO - 10.1016/j.jmro.2023.100139

M3 - Article

VL - 16-17

JO - Journal of Magnetic Resonance Open

JF - Journal of Magnetic Resonance Open

SN - 2666-4410

M1 - 100139

ER -